Galerius Valerius Maximianus (c. 258-311 CE) served as Roman emperor from 305-311 CE within the Tetrarchic system, initially as Diocletian's caesar. His military accomplishments include defeating the Sassanian Empire's Narseh at Satala (298 CE), potentially capturing Ctesiphon (299 CE), and successful campaigns against the Carpi (297 and 300 CE). Upon Diocletian's abdication, Galerius ascended to augustus status but faced numerous usurpers as the Tetrarchy collapsed. Despite his earlier opposition to Christianity, he ultimately ended the Diocletianic Persecution through his Edict of Serdica in 311 CE.